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diff --git a/README.rst b/README.rst new file mode 100644 index 0000000..8046204 --- /dev/null +++ b/README.rst @@ -0,0 +1,26 @@ +tmpoverlay +========== + +tmpoverlay is a small, almost-POSIX shell script to create tmpfs-backed +overlayfs mounts. See tmpoverlay --help for usage information. + +One important thing to note is that like any other Linux mount, an overlayfs +mount only affects new directory lookups. If a process has its current +directory or has files open inside the mount point, it continues to access the +original directory, not the overlaid one. Each process also has a cached root +directory pointer, which can only be modified by chroot (internally) or +pivot_root (globally). The pivot_root(2) and pivot_root(8) man pages should be +fully read and understood before using tmpoverlay to overmount root. + +POSIX compliance +---------------- + +With the following exceptions, tmpoverlay is intended to be functional on +POSIX-only shells: + +- ``getopt --`` is required for proper handling of options containing spaces +- ``mount -t overlay`` is obviously required +- ``getfattr`` is used for xattr copying but in case of failure, the system is + assumed to not support xattrs and setfattr is skipped. +- ``stat -c`` is used to obtain upperdir owner and permissions, because parsing + ls -l is nonsense. |